This research will quantitate the changes in leukocyte function, mechanical properties and morphology caused by an in vitro exposure to shear stress and foreign surfaces under precisely controlled viscometric conditions. With these damage levels ascertained, in vivo measurements of the hemodynamic change and morphological change caused by infusion of leukocyte suspensions will be taken. Cells which have undergone a known amount of in vitro trauma will be injected into experimental animals.